The goal is to get to a desirable population destination before tragedy overtakes us.

Humankind has contracting supporting resources (e.g. fossil fuels, soils, fisheries and minerals.)
By some calculations, within this century, our supporting resources will allow
less then 50-100 million people to exist at the reader’s of this text’s wellbeing.
And then, only if we are not squandering those resources — destroying each other and our infrastructure.

So the question remains, what process do we put in place to:
      a) get the population down to 50 to 100 million in 86 years?

      b) once we arrive at this new population,
            how does this process, stop reducing population?
                  (If the process continues to lower population at the rate it did to get to                         50-100 million,
                  it would quickly reduce our population below any number that would
                        allow species survival.)

                  Some rule like “less than two” or “one” is not a very good plan.
                        If those numbers become part of our global culture’s successful
                              advice to women, we are finished.

We all understand how hard it would be to get any number like 2 or 1 births-per-woman to be part of our culture. However, few of us have given consideration as to how hard it would be to undo it once the sustainable population was reached in 2100.

We need a process, for reducing population very quickly, that after it reaches its 50-100 million goal the process maintains that population.

A process that uses true fertility rate (number of children per woman) to achieve its stable population is not prudent. Whatever TFR was low enough to help make birth choices on the steep population down slope would leave residue in the birth decision process, that would wipe out the remaining 50-100 million people.

Our process has to be a bit more sophisticated than that. I have proposed a lottery to allow a fixed number of births each year during both the steep decline and the maintence time periods.I have outlined the mathematics of such a lottery in SKIL Note 81.

SKIL Note 81 ==> Today's "Dropping Fertility" is Meaningless and Harmful in Establishing Sustainability. It is futile to adjust human nature up or down on number of children. Let civil law determine the population that is sustainable.

Of course I do not want to minimize the difficulty of implementing such a lottery.
However, it is no more difficult that trying to implement a culture shift to
less than 2 or 1 or zero and back to “whatever births you want.” after your population is down to the sustainable value.